[JavaScript知识库]学习 阮一峰 ECMAScript 6 入门 代码小结-1

for (let codePoint of 'foo') {
  console.log(codePoint)
}

let greeting = `\`Yo\` World!`;
console.log(greeting);

let greetings=`${{i:5}}`
console.log(greetings);

const tmpl = addrs => `
  <table>
  ${addrs.map(addr => `
    <tr><td>${addr.first}</td></tr>
    <tr><td>${addr.last}</td></tr>
  `).join('')}
  </table>
`;

const data = [
    { first: '<Jane>', last: 'Bond' },
    { first: 'Lars', last: '<Croft>' },
];

console.log(tmpl(data));

let a = 5;
let b = 10;

function tag(s, v1, v2) {
    console.log(s[0]);
    console.log(s[1]);
    console.log(s[2]);
    console.log(v1);
    console.log(v2);
  
    return "OK";
  }
  
tag`Hello ${ a + b } world ${ a * b }`;
等同于
tag(['Hello ', ' world ', ''], 15, 50);

let total = 30;
let msg = passthru`The total is ${total} (${total*1.05} with tax)`;

function passthru(literals) {
    console.log(literals,arguments);

  let result = '';
  let i = 0;

  while (i < literals.length) {
    result += literals[i++];
    if (i < arguments.length) {
      result += arguments[i];
    }
  }

  return result;
}

console.log(msg);
let sender = '<script>alert("abc")</script>'; // 恶意代码
let message =
  SaferHTML`<p>${sender} has sent you a message.</p>`;

function SaferHTML(templateData) {
  let s = templateData[0];
  for (let i = 1; i < arguments.length; i++) {
    let arg = String(arguments[i]);

    // Escape special characters in the substitution.
    s += arg.replace(/&/g, "&amp;")
            .replace(/</g, "&lt;")
            .replace(/>/g, "&gt;");

    // Don't escape special characters in the template.
    s += templateData[i];
  }
  return s;
}

console.log(message);

console.log`123`

var s = "𠮷";

s.length // 2
s.charAt(0) // ''
s.charAt(1) // ''
s.charCodeAt(0) // 55362
s.charCodeAt(1) // 57271

let s = 'Hello world!';

s.startsWith('Hello') // true
s.endsWith('!') // true
s.includes('o') // true

console.log('aabbcc'.replaceAll('b', '_'));

console.log('abbc'.replaceAll('b', '$&'));

console.log('abbc'.replace(/(ab)(bc)/g, '$2$1'));

const str = '123abc456';
const regex = /(\d+)([a-z]+)(\d+)/g;

function replacer(match, p1, p2, p3, offset, string) {
  return [p1, p2, p3].join();
}

let a =str.replace(regex, replacer)
console.log(a);


const str = 'hello';
str.at(1) // "e"

console.log(str.at(1))

console.log(/^\uD83D/u.test('\uD83D\uDC2A'));//UTF-16
console.log(/^\uD83D/.test('\uD83D\uDC2A'));//UTF-8

var s = '𠮷';

console.log(/^.$/.test(s) );// false
console.log(/^.$/u.test(s)); // true

/\u{61}/.test('a') // false
/\u{61}/u.test('a') // true
/\u{20BB7}/u.test('𠮷') // true

console.log(Number('0b111'));

console.log(Number.isInteger(25.0));
function throwIfMissing() {
    throw new Error('Missing parameter');
  }
  
  function foo(mustBeProvided = throwIfMissing()) {
    return mustBeProvided;
  }
  
  foo('fff')

function doSomething(value = 070) {
    'use strict';
    return value;
  }

const doSomething = (function () {
    'use strict';
    return function(value = 42) {
      return value;
    };
  }());

console.log((new Function).name);

function foo() {
    setTimeout(() => {
      console.log('id:', this.id);
    }, 100);
  }
  
  var id = 21;
  
  foo.call({ id: 42 });

function Timer() {
    this.s1 = 0;
    this.s2 = 0;
    // 箭头函数
    setInterval(() => this.s1++, 1000);
    // 普通函数
    setInterval(function () {
      this.s2++;
    }, 1000);
  }
  
  var timer = new Timer();
  
  setTimeout(() => console.log('s1: ', timer.s1), 3100);
  setTimeout(() => console.log('s2: ', timer.s2), 3100);

function foo() {
    return () => {
      return () => {
        return () => {
          console.log('id:', this.id);
        };
      };
    };
  }
  
  var f = foo.call({id: 1});
  
  var t1 = f.call({id: 2})()(); // id: 1
  var t2 = f().call({id: 3})(); // id: 1
  var t3 = f()().call({id: 4}); // id: 1

function foo() {
    setTimeout(() => {
      console.log('args:', arguments);
    }, 100);
  }
  
  foo(2, 4, 6, 8)

(function() {
    return [
      (() => this.x).bind({ x: 'inner' })()
    ];
  }).call({ x: 'outer' });

s = 21;

const obj = {
  s: 42,
  m: () => console.log(this.s)
};

obj.m() // 21

function Fibonacci2 (n , ac1 = 1 , ac2 = 1) {
    if( n <= 1 ) {return ac2};
  
    return Fibonacci2 (n - 1, ac2, ac1 + ac2);
  }
  
  Fibonacci2(100) // 573147844013817200000
  Fibonacci2(1000) // 7.0330367711422765e+208
  Fibonacci2(10000) // Infinity

function currying(fn, n) {
    return function (m) {
      return fn.call(this, m, n);
    };
  }
  
  function tailFactorial(n, total) {
    if (n === 1) return total;
    return tailFactorial(n - 1, n * total);
  }
  
  const factorial = currying(tailFactorial, 1);
  
  factorial(5) // 120

function restricted(a,b) {
    console.log(restricted.caller);    // 报错
    console.log(restricted.arguments); // 报错
  }
  restricted(1,2);

function sum(x, y) {
    if (y > 0) {
      return sum(x + 1, y - 1);
    } else {
      return x;
    }
  }
  
  sum(1, 100000)

try {
    // ...
  } catch {
    // ...
  }

const arr = [
    ...(x > 0 ? ['a'] : []),
    'b',
  ];

  console.log(arr);

console.log([...'hello']);

Number.prototype[Symbol.iterator] = function*() {
    let i = 0;
    let num = this.valueOf();
    while (i < num) {
      yield i++;
    }
  }
  
  console.log([...5]) // [0, 1, 2, 3, 4]

let map = new Map([
    [1, 'one'],
    [2, 'two'],
    [3, 'three'],
  ]);
  
  let arr = [...map.keys()]; // [1, 2, 3]

Array.from('hello')
// ['h', 'e', 'l', 'l', 'o']

let namesSet = new Set(['a', 'b'])
Array.from(namesSet) // ['a', 'b']

function typesOf () {
    return Array.from(arguments, value => typeof value)
  }

  console.log(typesOf(null, [], NaN));

  Array.of(3, 11, 8)

['a', 'b', 'c'].fill(7)

let letter = ['a', 'b', 'c'];
let entries = letter.entries();
console.log(entries.next().value); // [0, 'a']
console.log(entries.next().value); // [1, 'b']
console.log(entries.next().value); // [2, 'c']

const contains = (() =>
  Array.prototype.includes
    ? (arr, value) => arr.includes(value)
    : (arr, value) => arr.some(el => el === value)
)();
contains(['foo', 'bar'], 'baz'); // => false

console.log([1, 2, [3, 4]].flat());

console.log([1, 2, [3, [4, 5]]].flat(2));

console.log([1, 2, , 4, 5].flat());

[2, 3, 4].flatMap((x) => [x, x * 2])

const cart = {
    _wheels: 4,
  
    get wheels () {
      return this._wheels;
    },
  
    set wheels (value) {
      if (value < this._wheels) {
        throw new Error('数值太小了！');
      }
      this._wheels = value;
    }
  }